Pipeline pigs are used in a wide range of different industrial settings, typically either for the cleaning or surveying of pipelines. In terms of cleaning, pigs are usually used to push or scrape out remaining product or material in the pipeline, helping to significantly reduce the quantity of cleaning fluid required to purge and flush remnants out before a subsequent manufacturing step, and in some instances, helping to recover valuable product from the line. An effective pigging system can lead to improvements in waste management, as well as shorten the time intervals required between process steps.
The requirement for high standards of quality and hygiene in the food industry and especially in the pharmaceutical industry, where aseptic processing may be required has led to the development of pigging systems in which the pig itself can be autonomously cleaned after use without its physical removal from the system. A ‘clean-in-place’ set-up enables the pig to be cleaned and readied for a subsequent redeployment without the risk of introducing contaminants into an otherwise sterile pipeline environment.
Pipeline pig launching stations with integrated cleaning stations or functions are known in the art. Typically, the pigs are held in place by a pig-catching element which may or may not also be part of the mechanism for launching the pig into the pipeline.
However, complete cleaning of pigs held in pig traps can be difficult to achieve, due to limited accessibility of the cleaning fluid especially to areas of the pig in contact with the trap. Prolonged cleaning times and thus increased quantities of cleaning fluid may consequently be required, especially to remove materials strongly adhered or compacted onto the surface of the pig. Certain forms of pigs, e.g. those with ribs and those which have generally less accessible surfaces may also be more difficult to clean.
GB2348939 describes a pipeline pig launching trap with a clean-in-place arrangement wherein the pig can be subjected to a surrounding swirling action of cleaning fluid. The system is described as being particularly effective for cleaning pipeline pigs of the cylindrical form provided with groups of closely spaced resilient discs. In this apparatus, cleaning fluid enters the pig trap through a laterally extending inlet pipe connection which is merged, in a dovetail configuration, to a cylindrical body part of the trap. With such an arrangement, the fluid enters the cylindrical body tangentially, causing it to surround the full length of the pig with a swirling action. Cleaning fluid is drained, depending on the embodiment of the apparatus, through a lower-situated outlet pipe connection that is axially parallel or axially perpendicular to the inlet pipe connection. The pig trap is vertically upstanding, so that when the pig is positioned for cleaning, i.e. at its lower-most position, there is contact to a rotatable launch cam or push rod component.
It is the object of the invention to provide an improved pig launching station for a clean-in-place system which overcomes at least one of the problems and limitations associated with prior art stations, or which enables a more effective pig cleaning. Another object is to provide an improved method of cleaning a pipeline pig. Other objects will become clear on the basis of the description and the claims